JP2679270B2 - Permanent magnet type erasing head and its magnetizing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet erasing head mainly used for erasing data recorded on a magnetic tape for audio and the like, and a magnetizing device therefor.

2. Description of the Related Art Generally, a permanent magnet type erasing head has a shape in which a magnetic material is provided on a required portion of a tape running surface, and a current is applied to a magnetizing yoke and a magnetizing coil provided so as to face the magnetic material. A magnetic field is generated to magnetize the magnetic field, and a typical conventional example will be described with reference to the accompanying drawings. FIG. 5 shows a process of magnetizing the permanent magnet type erasing head. The magnet portion provided in the erasing head main body 13 is shown in FIG.
Magnetizing yoke processed into a shape that closely adheres to the tape running surface of 14
15, magnetizing coils 16 and 17 provided on the magnetizing yoke 15 are connected in series, and a current is applied through a magnetizing power source 18 to generate a magnetic field as shown in FIG. The part 14 was magnetized. The surface condition of the magnet part 14 after magnetization is
These are shown in FIGS. FIG. 6 (a) shows the state of the magnetic poles. In this conventional example, N pole → S along the tape running direction.
It is a combination of poles. The strength of the magnetic field is in a state in which the north pole component 19 is generated in the direction and the south pole component 20 is generated in the direction as shown in FIG. Also, the N pole
19 and S pole 20 are commercialized with a configuration in which switching field portions ρ21 and η22 are induced and generated before and after the S pole 20, respectively.

However, in the conventional permanent magnet type erasing head, as shown in FIG. 6 due to variations in product size / characteristic surface and variations in current / magnetization yoke and product adhesion state during magnetization. A variation occurs in the magnetic field strength after magnetization shown in (b).
In particular, the maximum magnetic field strength A of the magnetic pole portion and the maximum magnetic field strength B of the reversal magnetic field portion on the exit side in the tape running direction, which are magnetic field strengths important as erasing characteristics, will be described with reference to FIG. The ratio of the maximum magnetic field strength A of the magnetic pole part to the maximum magnetic field strength B of the reversal magnetic field part is shown as B / A as the magnetic field strength ratio, and the recording / playback level for that magnetic field strength ratio is measured and compared. In addition, the magnetic field strength ratio B / A dropped sharply at the boundary of 0.1, and the defect largely deviated from the non-defective product range shown by the shaded area in the figure, and the contents included unstable factors in terms of quality. Also, with this configuration, the magnetic field strength ratio B / A does not change even if the conditions are changed.
Was saturated at about 0.4 at most, and could not be more than that.

The present invention provides a permanent magnet type erasing head and a magnetizing device for the same, which can eliminate the above-mentioned conventional drawbacks and exhibit stable recording and reproducing levels in terms of quality.

Means for Solving the Problems In order to solve the above problems, the present invention provides a reversal magnetic field portion having a magnetic field strength ratio of 0.4 to 0.7 with respect to the final pole tape exit side magnetic pole portion on the final pole tape exit side in the tape running direction. Is provided.

Action With this configuration, the magnetic field strength of the reversal magnetic field portion can be stabilized at a high level, and the quality can be significantly improved.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows a step of magnetizing the permanent magnet type erasing head. Since the tape sliding surface (R-shaped portion) of the magnet portion 2 provided in the erasing head body 1 is magnetized, A magnetizing device having a shape facing the moving surface is used. As shown in FIG. 1, the magnetizing device includes a magnetizing yoke 3 provided with a main magnetizing portion forming a tape sliding surface, and an auxiliary magnetizing member which is characteristic of the present invention and which comes into contact with the side of the final pole tape outlet side in the tape running direction. An integrated product provided with a magnetic portion 12, and for the purpose of forming each magnetic pole portion, a main magnetizing coil 4,5 and an auxiliary magnetizing coil 6 are provided in each magnetic pole portion, and these magnetizing coils 4 to 6 are connected in series. It is configured to be connected and magnetized by applying a current from a magnetizing power supply 7. The surface condition of the magnet portion 2 after magnetization is shown in FIGS. 2 (a) and 2 (b). FIG. 7A shows the state of the magnetic poles, which is N along the tape running direction.
The main pole portion is a combination of poles and S poles. The intensity of the magnetic field is in a state in which the north pole component 8 is generated in the direction and the south pole component 9 is generated in the direction as shown in FIG.
Inversion magnetic field portions ρ10 and η11 are induced and generated before and after the N-pole component 8 and the S-pole 9, respectively.

As described above, the magnetizing device for the permanent magnet type erasing head according to the present invention efficiently stabilizes the magnetic field strength of the reversal magnetic field portion at a high level, which is a conventional defect, and as shown in FIG. The flow of magnetic flux is also focused on the side of the final pole tape exit side in the tape running direction via the auxiliary magnetizing portion 12 provided in the magnetic flux flowing and focusing of the conventional magnetizing device shown in FIG. It is different. As a result, when erasing characteristics are viewed, when the ratio of the maximum magnetic field strength A'of the magnetic pole portion and the maximum magnetic field strength B'of the reversal magnetic field portion shown in FIG. The ratio is about 0.4-0.7,
It was confirmed that even if the current applied to the magnetizing device was varied, the magnetic field strength ratio was stable within the range of 0.4 to 0.7. As a result, as shown in Fig. 5, it is possible to stabilize the recording / generating level with respect to the magnetic field strength ratio B '/ A' with a sufficient margin, and a large contribution can be obtained with easy means. is there.

EFFECTS OF THE INVENTION Since the permanent magnet erasing head and the magnetizing device thereof according to the present invention are configured as described above, the final pole tape outlet side in the tape running direction is 0.
The recording / playback level is stable in the reversal magnetic field part generated at a magnetic field strength ratio of 4 to 0.7, and the quality can be greatly improved, and the magnetizing itself is positioned by the auxiliary magnetizing part compared to the conventional one. It is possible to obtain the effect that it can be done reliably and efficiently, and it has great industrial value.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a magnetizing device for a permanent magnet type erase head according to the present invention, and FIGS. 2 (a) and 2 (b) are magnetized states of a permanent magnet type erase head obtained thereby. FIG. 3 is an explanatory view showing the flow of magnetic flux generated by the magnetizing device of the present invention, and FIG. 4 is a characteristic diagram of the magnetic field strength ratio and the recording / playback level of the product of the present invention. FIG. 5 is a front view of a magnetizing device for a conventional permanent magnet type erasing head, and FIG.
(A) and (b) are explanatory views of a magnetized state of the permanent magnet type erasing head, FIG. 7 is a characteristic diagram of the magnetic field strength ratio and recording / reproducing level, and FIG. It is a front view which shows the flow of the magnetic flux of an apparatus. 1 ... Erase head main body, 2 ... Magnet part, 3 ... Magnetizing yoke, 4,5 ... Main magnetizing coil, 6 ... Auxiliary magnetizing coil, 7
... Magnetizing power supply, 8 ... N-pole component, 9 ... S-pole component, 10 ...
… Reversing magnetic field part ρ, 11 …… Reversing magnetic field part η, 12 …… Auxiliary magnetizing part.

Claims (2)

(57) [Claims] 1. A reversal magnetic field portion having a magnetic field strength ratio of 0.4 to 0.7 with respect to the magnetic pole portion on the final pole tape exit side is magnetized at the final pole tape exit side in the tape running direction of a magnet portion incorporated in an erasing head body. Permanent magnet type erasing head provided. 2. A main magnetizing portion of a permanent magnet type erasing head which is provided with a magnet portion on the tape running surface of the erasing head body so as to be in close contact with the tape running surface, and a permanent magnet type erasing head in the tape running direction. A magnetizing yoke integrally provided with an auxiliary magnetizing portion in contact with the side surface on the exit side of the final pole tape, and a magnetizing coil wound around the main magnetizing portion and the auxiliary magnetizing portion of the magnetizing yoke. A permanent magnet type in which a reversal magnetic field with a magnetic field strength ratio of 0.4 to 0.7 with respect to the main magnetized portion is generated at the outlet side in the tape running direction by applying a current to the magnetizing coil to magnetize the magnet portion. Magnetizing device for erasing head.